This invention relates to surface-treating compositions comprising certain nitrogen ylides, ammonioamidates, which are surface-active agents and are able to exist in zwitterionic (ylide) form or in cationic form.
Quaternary ammonium compounds having at least one long chain (about C.sub.8 upwards) hydrophobic radical in the molecule have long been known. They are useful as cationic surface-active agents (so called "invert soaps"), as textile softening agents and as bactericides. When intended for use as surface-active agents, the long chain group usually has from about 12 to about 20 carbon atoms. When intended for use as textile softeners, long-chained compounds, for instance having about 16 to 22 or more carbon atoms, are preferred, especially compounds possessing two long chain groups. Typical examples include: octadecyldimethyl benzyl ammonium chloride, octadecyltrimethyl ammonium chloride, distearyl dimethyl ammonium chloride, the corresponding bromides, and many others of similar structure.
These compounds, particularly distearyl dimethyl ammonium chloride, have been used commercially in textile softening compositions intended to be added to the last rinse water after a conventional washing process, and attempts have been made to use them in detergent compositions intended to be combined washing and textile softening agents.
Being cationic, these substances ordinarily react with anionic detergents to form insoluble substances, and so their use in the presence of anionic detergents is not normally practicable. Furthermore, they have a strong affinity for fabrics, especially cotton and wools, a fact which plays an important part in their effectiveness as textile softeners and bactericides, but also has the effect that they are generally not completely washed out of the fabric in a succeeding wash. They therefore tend to build up on repeatedly washed fabrics, and may thus impair the rewetting properties of the fabrics, tend to cause discoloration, fiber snagging and even cause undesirable odors.
Other quaternary ammonium compounds constitute the known zwitterionic surface-active compounds, for example, the long-chain carboxylic betaines, sulpho-betaines, sulphato- and sulphito betaines. These compounds are valuable wetting agents and detergents. They are internal salts and, therefore, do not react with the metal ions present in hard water, especially calcium ions, and thus are almost unaffected by water hardness. For the same reason, they are compatible with anionic, cationic and nonionic detergents. Their affinity for and wetting effect upon certain highly hydrophobic fibers, such as polyamine and polyester fibers, renders them particularly valuable for removing certain types of soils, especially greasy soils, from these materials. They are also remarkably effective in cleaning cotton fabrics soiled with dirt which contains clay particles. However, they are not strongly substantive to fabrics and are not very effective textile softening agents. These known betaine and betaine-like compounds exist in zwitterionic form over a wide range of pH. In relatively strongly acid conditions they do become cationic, but the necessary acidity is outside the practical range for washing fabrics or human beings.
The present invention is concerned with a class of surface-active agents which are cationic under neutral or weakly acid conditions, and are zwitterionic under weakly alkaline conditions. Thus, if present at the ordinary pH of a rinsing operation in an aqueous solution (which need not, of course, necessarily in fact constitute the rinse after a wash) they are largely in cationic form and are effective as textile softening agents substantive to fabrics. Under the ordinarily alkaline conditions of a subsequent conventional washing operation, they convert to a zwitterionic form, and thus are substantially removed from the fabrics. When so removed, they are compatible with the detergent composition and may even enhance its effectiveness.